Apparatus for separating solid materials of different specific gravities by means of a suspension



June 2, 1959- V DRU 2,889,043

APPARATUS FOR SEPARATING SOLID MATERIALS OF DIFFERENT SPECIFIC GRAVITIESBY MEANS OF A SUSPENSION Filed March 29, 1956 4 Sheets-Sheet 1L INVENTORMAZCEL 086 ATTORNEY June 2, 1959 DRU APPARATUS FOR SEPARATING SOLIDMATERIALS OF DIFFERENT SPECIFIC GRAVITIES BY MEANS OF A SUSPENSION FiledMarch 29, 1956 4 Sheets-Sheet 2 INVENTOR MA .2651. 02

ATTORNEY June 2, 1959 M R DRL', 2,889,043

APPARATUS FOR SEPARATING SbLID MATERIALS OF DIFFERENT SPECIFIC GRAVITIESBY MEANS OF A SUSPENSION Filed March 29, 1956 4 Sheets-Sheet 3 INVENTORMA 8 CEL DZZ/ BY mmk ATTORNEY June 1 M. R. DRU 2,889,043

APPARATUS FOR SEPARATING SOLID MATERIALS OF DIFFERENT SPECIFIC GRAVITIESBY MEANS OF A SUSPENSION Filed March 29, 1956 4 Sheets-Sheet 4 if BYmfiwh ATTORNEY United States l atent O 2,889,043 APPARATUS FORSEPARATING SOLID MATE- 'RIALS OF DIFFERENT SPECIFIC GRAVITIES BY MEANSOF A SUSPENSION Marcel Roger Dru, Fontainebleau, France, assignor tSociete Jaruza A.G., Chur, Zurich, Switzerland, a Swiss companyApplication March 29, 1956, Serial No. 574,858 Claims priority,application France March 30, 1955 2 Claims. (Cl. 209-1725) Thisinvention relates to apparatus for separating solid materials and hasmore particular reference to apparatus for separating solid materials ofdifferent specific gravities by means of a suspension.

One object of the present invention is to provide a novel and improvedapparatus for separating solid materials of different specific gravitiesby means of a suspen sion, as for example, in coal washinginstallations, for separating slate, sand or other heavy constituentsfrom the coal.

Another object of the present invention is to provide apparatus, ascharacterized above, including a sedimentation vat into and throughwhich the dense liquid flows so that the float or light weight productspass over the overflow sill or weir of the vat with some of the denseliquid, an inclined casing positioned at one side of the vat with thelower end portion of the casing forming the bottom portion of the vat toreceive the sink or heavy settled products, a lifting wheel mounted inthe inclined casing for raising the solid material up to an evacuationpoint, and an inclined chute having its upper receiving end positionedto receive the heavy solids as they are evacuated from the lifting wheeland its lower end positioned to discharge the heavy products gravityflowing therethrough onto a divided draining screen which receives thefloat products as they pass over the overflow sill of the vat.

Another object of the invention is to provide apparatus, ascharacterized above, wherein the sedimentation vat is divided into aplurality of separating compartments, each water-tight with respect tothe other and adapted to hold dense liquids of diflerent specificgravities, and wherein means are provided for each compartment forevacuating the heavy settle solids therefrom, including an inclinedcasing positioned at one side of the vat with the lower end portion ofthe casing forming the bottom portion of its respective compartment toreceive the heavy solids settled therein, a lifting wheel mounted in theinclined casing for raising the solid material up to a discharge point,and wherein a plurality of chutes are provided, each positioned toreceive the raised solids from one of said compartments, with the chutewhich receives the raised heavy solids from the compartment adapted tocontain the dense liquid of the highest specific gravity positioned todischarge the heavy products passing therethrough onto a separateddraining screen which receives the float products from all of thecompartments, and with the remaining chutes positioned so that theraised solids from each of the compartments will be discharged into thenext compartment which is adapted to hold dense fluid of a higherspecific gravity than the compartment from which the heavy products wereraised.

Another object of the invention is to provide apparatus, ascharacterized above, wherein the mechanical parts are so constructed asto minimize the abrasive action of the dense liquids.

A further object of the invention is to provide apparatus for separatingsolid materials of diflerent densities by means of a suspension, whichis simple and inexpensive in construction and eflicient in operation.

2,889,043 Patented June 2, 1959 ice Other objects and advantages of theinvention will appear in the following specification when consideredwith the accompanying drawings, wherein:

Fig. 1 is a vertical, transverse section of one embodiment of apparatusconstructed in accordance with the present invention;

Fig. 2 is a full elevational view taken on the line 2-2 of Fig. 1,looking in the direction of the arrows;

Fig. 3 is a view similar to that shown in Fig. 1, but showing a modifiedform of apparatus;

Fig. 4 is a full elevational view taken on the line 4-4 of Fig. 3,looking in the direction of the arrows;

Fig. 5 is a vertical sectional view taken on the line 55 of Fig. 4,showing the construction of the lifting wheel;

Fig. 6 is aview similar to that shown in Fig. 1, but showing anothermodified form of apparatus;

Fig. 7 is a full elevational view taken on the line 77 of Fig. 6,looking in the direction of the arrows;

Fig. 8 is a vertical sectional view taken on the line 8-8 of Fig. 7,showing the construction of the blades of the lifting wheel;

Fig. 9 is a view similar to that shown in Fig. 1, but showing anothermodified form of apparatus; and

Fig. 10 is a full elevational view taken on the line 10-10 of Fig. 9,looking in the direction of the arrows.

The present invention is an improvement over that shown and. claimed inmy prior Patent No. 2,678,727, granted on May 18, 1954, for SeparatingSolid Materials by Suspension.

My aforesaid prior patent discloses apparatus for separating solidmaterial of different specific gravities into two classes and comprisesa large vat into which dense liquid and the material to be separated aredelivered and wherein a liquid level is maintained so that the float orlighter products are evacuated by overflowing with the liquid while thesink or heavier products fall to the bottom, from where they are removedby means of a rotating paddle wheel mounted in an inclined annularcasing arranged at one side of the vat. The raised products beingevacuated through an opening in the top portion of the annular casing.

The present invention provides improved means for raising the sink orheavy products and provides for these raised products to be dischargedonto a divided draining screen positioned to receive the float orlighter products as they pass over the overflow sill of the vat.

The present invention further provides means for separating the materialto be treated into more than two classes of diflerent specific gravitiesby dividing the sedimentation vat into a plurality of separateseparating compartments with each compartment water-tight with respectto the other compartments and adapted to contain a dense liquid of apredetermined specific gravity, and with means provided for raising anddelivering the sink or heavy products from one compartment to acompartment filled with dense liquid of a higher specific gravity, andwith the float products from all of the compartments being deliveredonto separate parts of a divided draining screen and with the heavyproducts from the compartment containing the dense liquid of the highestspecific gravity, being discharged onto a separate section of thedraining screen which receives the float products from all of thecompartments.

Referring now to the drawings, there is illustrated in Figs. 1 and 2,one embodiment of apparatus, constructed in accordance with the presentinvention. As there shown, the apparatus comprises an elongatedgenerally rectangular sedimentation vat or wash box 10 having anoverflow sill or weir 11 on its outlet end and into the opposite end ofwhich are delivered the dense liquid and the solid material to beseparated by any suitable usual means (not shown); an inclined open-topcasing 12 post 3 tioned at one side of the vat and with its lower endopen iug into and forming the'bot't'om'pertion of the vat; an inclinedshaft 13 extending up through the bottom wall of the casing in adirection normal, to the plane of inclination .of the casing to the vat;a lifting wheel, indicated generally at 14, mounted on said shaft withinsaid casing; a divided draining screen 15 positioned adjacent theoverflow sill of the vat to receive the float products discharged'thereover onto one side of the screen; and a stationary chute 16 havingits upper end positioned to receive the heavy products as they aredischarged from the lifting wheel and its lower end positioned todischarge the heavy products passing therethrough onto the other side ofthe di ided draining screen.

The'sedimentation 'vat 10 is generally similar in construction to thevat shown'inmy. aforesaid patent. It is shown as'an elongated, generallyrectangular vat having vertical sidewalls 17, 18 anda-bott'om wall 19having oppositely inclined portions whichinerge into the bottom endportion of the inclined casing-12; 5 i

The inclined casing'12, whichhous'es thelifting wheel and helps form thebottom portionof the vat, is shown as having a comically shaped bottom"wall'20, through the apex of which the shaft 13 extends, the apex beingpositioned above the liquid level of the vat, and a side wall 21extending upwardly from the outer periphery of the bottom wall. A drainnipple 22, provided with a suitable closure member, is shown as beingconnected to the lower part of the casing 12 to permit the bottom of thevat and the casing to be cleaned out periodically. The lower portion ofthe bottom wall. of the casing, as indicated at 23, in effect forms aside wall of the vat. The side wall 17 of the vat adjacent the casingacts as a baflie member preventing the flow of the float or lighterproducts from the vat into the casing.

The lifting wheel 14 is shown as comprising an annular plate 24 havingan upstanding flange formed around its outer periphery forming an outerwall 25; a plurality of spokes or arms 26, each attached at its outerend to the bottom of the plate 24 and at its inner end to a hub fixed onthe shaft 13 for rotation therewith, and a plurality of curved blades 27secured to the upper surface of the plate 24 in circumferentially spacedrelation; the curvature of the blades being such that the spaces betweenadjacent blades form baskets opening in a radial direction with respectto the lifting wheel. The shaft 13 is journaled in suitable fixed upperand lower bearings 28 and 28', respectively, and is driven by anysuitable means, such as a worm wheel 29 fixed on the lower end of theshaft and driven bya worm 30 on a shaft 31 adapted to be driven by anysuitable means (not shown).

The inclination of the casing 12, the downward inclination of the arm 26of the lifting wheel, and the height of the'upper bearing of the shaftare such that the upper bearing is above the water level of the denseliquid in the tank.

The lifted heavy products are prevented from prematurely sliding out ofthe baskets by fixed guiding means positioned around the inner peripheryof the lifting wheel. The guiding means is shown as being in the form ofan interrupted cylinder 32 fixedly held in position adjacent the innerperiphery of the lifting wheel, as by means of a plurality of supportingarms 33 connecting the cylinder to the outer side wall 21 of the casing12. i

The draining screen 15 may be of any usual construction and is shown ascomprising an elongated perforated or reticulated bottom wall member 34-having vertical side walls 35, 36 and having its screening surfacedivided into two parts by a longitudinally extending vertical wallmember 37. The draining screen is mounted adjacent to the discharge endof the vat below the overflow sill or weir in position to receive theoutflow liquid and float products onto the left hand side of its dividedscreening surface, as seen in Fig. 2. i

The chute 16 may be of any suitable usual CQ ISU' JP tion. It is shownas a trough-like structure having a closed bottom 38 and upstanding sidewalls 39, 40'. The chute has its upper receiving: end fixedly attachedto the interrupted ends of the cylinder 32 and with its bottom wallprojecting below the annular plate 24 of the lifting wheel, in positionto receive the heavy products as they fall from the baskets in thelifting wheel, through the interruption in the cylinder 32, as itrotates. The chute has its lower discharge end positioned to dischargethe heavy products gravity flowing therethrough onto the right hand sideof the divided surface of the draining screen, as viewed in Fig. 2.

In Figs. 3, 4 and 5, there is illustrated a modified form of theapparatus. In this modification, the vat 10' with its overflow sill or.weir 11,-the inclined casing 12', the shaft 13' with its mounting anddrive mechanism, and the divided draining screen 15', are all identicalin. construction to the construction of t he corresponding parts. of themodification shown in'Fig's. l and 2. The lifting wheel 14 is shown ascomprised of an annular channel member having a bottom wall 41 and innerand outer cylindrical side walls 42, 43 supported by a plurality ofradial arms or spokes 44, each connected at one end to a hub fixed onthe shaft 13 and the other end to the bottom wall of the channel member.A plurality of circumferentially spaced blades 45 curve upwardly fromthe bottom wall of the channel with their outer ends curving inwardlytoward the interior of the wheel and ending in discharge spouts 46positioned above and extending slightly beyond the inner wall 42 of thechannel member. The blades 45 divide the channel into a plurality ofbaskets for receiving the heavy settled products.

In this particular modification the chute 16' is generally similar tothe chute 16 shown in Fig. I, but has its upper receiving end positionedto receive the heavy products when they start to slide out of thebaskets of the lifting wheel which is a position reached by the basketsafter they have passed the highest point in their path of rotation. Theupper end portion of the chute may be fixedly supported, as by means ofsupport members 47 connecting the chute to the outer wall 21' of thecasing 12. The lower discharge end of the chute 16' is positioned todischarge the heavy products gravity flowing therethrough onto one sideof the divided draining screen 15 In Figs. 6, 7 and 8, there isillustrated another modified form of the apparatus. In thismodification, the vat 10", the inclined casing 12", the shaft 13" withits mounting and drive mechanism, and the divided draining screen 15",are all identical in construction to the construction of thecorresponding parts of the modification shown in Figs. 1 and 2. Thelifting wheel 14 is shown as comprising a stationary annular plate orbase member 48 having an upstanding flange around its outer peripheryforming a cylindrical outer wall 49. The annular base member 48 isfixedly mounted within the inclined casing 12", as by means of aplurality of circumferentially spaced support members 50 connecting thewall 49 of the base member to the wall 21'? of the casing; and arotatable cylindrical member 51 mounted within the casing 12" andconnected for rotation with the shaft 13" by means of a plurality ofspokes or arms 52 each connected at one end to the cylindrical memberSl'and at the other end to a hub fixed on the shaft 13"; The

cylindrical member 51 forms a movable wall slightly spaced from theinner periphery of the base member 48 and carries a plurality ofcircumferentially spaced curved scraper blades 53 extending in scrapingposition over the upper surface of the base member 48 with the bottomedge of the blades spaced slightly above the upper surface of the basemember and with the'outer edges of the blades slightly spaced from thecylindrical wall 49 of the base member.

A portion of the fixed outer wall 49 of the base mem-' ber 48 is cutaway to provide an opening 54 through which the heavy products lifted bythe blades 53 are discharged when the heavy products have reached aposition where they start to slide out of the baskets formed by thespace between adjacent blades, which position is a position reached bythe baskets after they have passed the highest point in their path ofrotation.

The upper receiving end of a chute 16'' having a bottom wall 55 andupstanding side walls 56, 57, is fixedly connected to the ends of theside edges of the opening 54 in the wall 49 of the annular base member43 so that the heavy products will be received in the chute as theyslide outwardly through the opening 54 in the wall 49. The chute 16 thencurves downwardly and across the front of the inclined casing 12 withits lower discharge end positioned to discharge the heavy productsgravity flowing therethrough onto the divided draining screen 15".

In Figs. 9 and 10, there is illustrated still another modification ofthe apparatus. In this particular modification, the apparatus is shownas comprising an elongated generally rectangular sedimentation tank orvat 58 divided into separate inner and outer elongated wash boxes orseparating compartments 59 and 60, respectively, which are water-tightwith respect to each other; a pair of inclined casings 61, 62 positionedat one side of the vat in vertically spaced superposed relation with theupper casing 61 having its lower end opening into and forming the bottomportion of the inner compartment 59 and with the lower casing 62 havingits lower end opening into and forming the bottom portion of the outercompartment 60; an inclined rotatable shaft 63 extending up through thebottom walls of both casings in a direction normal to the planes ofinclination of the casings to the vat; lifting Wheels 64, 65 mountedwithin the upper and lower casings 61, 62, respectively, are connectedto the shaft 63 for rotation therewith; a divided draining screen 66positioned adjacent the overflow sills of the two compartments 59, 60 toreceive the float products discharged thereover onto separate sectionsof the screen; a stationary chute 67 having its upper end positioned toreceive the heavy products as they are discharged from the lifting wheel65 and its lower end positioned to discharge the heavy products gravityflowing therethrough into the receiving end of the inner compartment 59;and a second stationary chute 68 having its upper end positioned toreceive the heavy products as they are discharged from the lifting wheel64, and its lower end positioned to discharge the heavy products gravityflowing therethrough onto one section of the divided draining screen 66.

The inner separating compartment 59 is shown as having vertical sidewalls 69, 70 and a bottom wall 71 having oppositely inclined portionswhich merge into the bottom end portion of the inclined casing 61.

The inclined casing 61, which houses the lifting wheel 64 and helps formthe bottom portion of the inner compartment 59, is shown as having aconically shaped bottom wall 72, through the apex of which the shaft 63extends, the apex being positioned above the liquid level of thecompartment, and a side wall 73 extending upwardly from the outerperiphery of the bottom wall. The lower portion of the bottom wall ofthe casing, as indicated at 74, in effect forms the inner side wall ofthe compartment. The side wall 69 of the inner compartment acts as abafie member preventing the flow of the float or lighter products fromthe compartment 59 into the casing 61.

The outer separating compartment 60 is shown as having a vertical outerside wall 75, a vertical inner side wall formed by the vertical sidewalls 70 of the inner compartment 59, and a bottom wall 76 havingoppositely inclined portions which merge into the bottom end portion ofthe inclined casing 62.

The inclined casing 62, which houses the lifting wheel 65 and helps toform the bottom portion of the outer compartment 60, is shown as havinga conically shaped bottom wall 77, through the apex of which the shaft63 extends, the apex being positioned above the liquid level of thecompartment, and a side wall 78 extending upwardly from the outerperiphery of the bottom wall. The space between the lower portions ofthe two casings 61, 62, in effect forms a compartment communicating withthe outer compartment 60 and the dense liquid from compartment 60 fillsthis space up to the same liquid level as exists in compartment 60.

The lifting wheel 64, which is rotatably mounted within the upperinclined casing 61, is shown as comprising an annular plate 79 having anupstanding flange formed around its outer periphery forming an outerwall 80; a plurality of spokes or arms 81 connecting the annular plate79 to a hub fixed on the shafts 63 for rotation therewith; and aplurality of curved blades 82 secured on the upper surface of the plate79 in circumferentially spaced relation, the curvature of the bladesbeing such that the space between adjacent blades forms a basket openinginwardly in a radial direction with respect to the lifting wheel.

The heavy products lifted by the wheel 64 are prevented from prematurelysliding out of the baskets by fixed guiding means positioned around theinner periphery of the wheel. The guiding means is shown as being in theform of an interrupted cylinder 83 fixedly held in position adjacent theinner periphery of the lifting wheel as by means of a plurality ofsupporting arms 84 connecting the cylinder to the outer side wall 73 ofthe upper casing 61.

The chute 63 which carries the heavy products raised by the liftingwheel 64 and deposits them on the divided draining screen 66, is shownas a trough-like structure having a closed bottom wall 85 and upstandingside walls 86, 87. The chute has its upper receiving end fixedlyattached to the interrupted ends of the cylinder 33 and with its bottomwall projecting below the annular plate 79 of the lifting wheel inposition to receive the heavy products as they fall from the baskets onthe lifting wheel through the interruption in the cylinder 83. The chutehas its lower discharge end positioned to dis charge the heavy productsgravity flowing thereflhrough onto one side of the divided drainingscreen 66.

The lifting wheel 65, which is rotatably mounted within the lowerinclined casing 62, is shown as comprising an annular plate 88 having anupstanding flange formed around its outer periphery forming an outerwall 89; a plurality of spokes or arms 90 connecting the annular plate38 to a hub fixed on the shaft 63 for rotation therewith; and aplurality of curved blades 91 secured on the upper surface of the plate88 in circumferentially spaced relation, the curvature of the bladesbeing such that the space between adjacent blades forms a basket openinginwardly in a radial direction with respect to the lifting wheel.

The heavy products lifted by the wheel 65 are prevented from prematurelysliding out of the baskets by fixed guiding means positioned around theinner periphery of the wheel. The guiding means is shown as being formedby an upper cylindrical portion 92 of the side wall 73 of the upperinclined casing 61. This upper cylindrical portion 92 merges into thebottom wall member 71 of the inner separating compartment 59 and has aninterruption formed therein in its upper portion forming an opening 93through which the heavy products lifted by the wheel are discharged ontothe chute 67.

The chute 67, which receives the heavy products raised by the liftingwheel 65 and deposits them into the receiving end of the separatingcompartment 59, is shown as a trough-like structure having a closedbottom wall 94 and upstanding side walls 95, 96. The chute has its upperreceiving end fixedly attached to the end of the opening 93 formed inthe cylindrical portion 92 of the side wall 73 of the upper inclinedcasing 61 and with its bottom wall projecting below the annular plate 88of the lifting wheel, inposition to receive the heavy prod ucts as theyfall from the baskets in the lifting Wheel through the opening 93. Thechute has its lower discharge end positioned to discharge the heavyproducts gravity flowing therethrough into the receiving end of theseparating compartment 59.

The shaft 63 is journaled in suitable fixed upper and lower bearings 97,98, respectively, and is driven by any suitable means, such as shown inFig. 1, for driving the corresponding shaft 13.

The draining screen 66 is similar in construction to the draining screenshown in the modification illustrated in Fig. 2, and is divided intothree sectons by longitudinally extending upstanding wall members 100,101, 102, and 103, one for receiving the float products as they aredischarged over the overflow sill 104- of the separating compartment 60,one for receiving the float products as they are discharged over theoverflow sill 105 of the separating compartment 59, and one forreceiving the heavy products discharged by the chute 68.

The blades of the lifting wheel 64 are so curved that the liftedproducts slide inwardly toward the center of the wheel before reachingthe highest point in the path of rotation of the wheel and the blades ofthe lifting wheel 65 are so curved that the lifted products slideinwardly toward the center of the wheel after passing over the highestpoint in the path of rotation of the wheel. Also, the dense liquidlifted by the baskets in each wheel will drain back into the compartmentfrom which it was lifted through the space between the guiding means forretaining the heavy products in the baskets and the inner periphery ofthe wheel, thus preventing any mixing of the dense liquid in the twoseparating compartments.

The operation of the various modifications of the apparatus, asillustrated in Figs. 1 to 8, inclusive, is believed apparent. The vat isfilled with a dense liquid or suspension, such for example, as a mixtureof fine sand and water, up to a desired liquid level. The raw materialsto be treated fall into the front end of the vat. products or lightfractions are discharged over the overflow sill or weir with theoverflow of dense liquid and fall onto the draining screen. The sinproducts or heavy fractions fall into the bottom of the series ofbaskets of the lifting wheel and are lifted by the wheel, as it rotates,and, at an elevated point in the path of rotation, slide on the curvedblades and the bottom of the wheel into the chute mounted to receivethem, and are discharged by the chute onto one side of the drainingscreen near the light fractions discharged thereon.

In the apparatus shown in Figs. 9 and 10, considering the case of coalwashing, the operation takes place as follows:

The raw coal (consisting of coal, middlings and shales) falls into theouter compartment 60 where a first separation is effected.

The treated coal, referred to as washed coal, passes above the weir 104with some overflow of dense liquid and is discharged upon the outersection of the draining screen 66. The mixture of middlings and shalesfalls to the bottom, into the rotating series of baskets formed by theblades 91 of the lifting wheel 65. They drain during lifting and, afterpassing beyond the highest point in the path of rotation of the wheel,fall into the chute 67 which conveys them to the inner compartment 59containing dense liquid of a higher specific gravity than that in thecompartment 60.

In this wash box compartment 59, the mixture of middlings and shales isseparated as follows:

The middlings float, are driven by the liquid flow and leave theapparatus above the weir 105, with the overflow of liquid; they aredischarged onto the central section of the partitioned draining screen66.

The shales sink in the series of baskets formed by the blades 82 of thelifting wheel 64, are lifted, and, before 8 reaching the highest pointin the path of rotation, slide into the chute 68, which discharges themoutside the apparatus onto the inner section of the draining screen 66.

As will be seen from the above description, the raw mixture entering theapparatus is separated into three fractions by two separating gravities.These fractions travel automatically and are finally discharged inparallel directions and in the same area, opposite the entrance openingof the raw mixture.

Obviously, the invention is not restricted to the particular embodimentthereof herein shown and described, but is capable of variousmodifications within the scope of the appended claims.

What is claimed is:

1. In an apparatus for separating solid materials having differentspecific gravities, comprising an elongated sedimentation vat forholding a body of dense liquid, said vat having an overflow sill alongone end over which the light fraction is discharged with overflow denseliquid; a draining screen positioned below the overflow sill, saiddraining screen being divided into a plurality of separatelongitudinally extending sections with one section positioned to receivethe light fractions discharged with the overflow dense liquid; aninclined open top casing positioned at one side of said vat with itslower end opening into and forming the bottom portion of the vat toreceive the heavy settled fraction, the side wall of the vat adjacentthe casing acting as a baflle member preventing the flow of the lightfraction from the vat into the casing; a shaft extending upwardlythrough the bottom of said casing in a direction normal to the plane ofinclination of said casing to said vat; a lifting wheel including anannular plate having an upstanding flange around its outer peripheryforming an outer wall mounted in said casing and fixedly connected tosaid shaft for rotation therewith by a series of supporting arms, saidlifting wheel carrying a plurality of circumferentially spaced bladespositioned adjacent its outer periphery with the spaces between theblades forming baskets in which the heavy fractions are received whenthey sink into the bottom of the vat and are lifted by the basketsas'the wheel rotates, said blades being' baskets at an elevated point inthe path of rotation of the baskets and extending downwardly across theopen top of said inclined casing with its lower discharge end positionedadjacent to and at a height substantially equal to that of said overflowsill to discharge the heavy fractions gravity flowing therethrough ontoanother section of said draining screen adjacent the light fractionsdischarged thereon; and means for rotating said shaft and said wheel forraising said heavy fractions up from the bottom of the vat.

2. Apparatus as set forth in claim 1, including an interruptedcylindrical member fixedly mounted within said casing with its outersurface slightly spaced from the inner periphery of said annular plateto prevent the lifted heavy fractions from prematurely sliding out ofsaid baskets and wherein the upper receiving end 'of said chute isconnected to the end of the interruption in said cylinder so that theheavy fractions will slide through the opening formed by theinterruption into said chute.

References Cited in the file of this patent UNITED STATES PATENTS2,678,727 Dru May 18, 1954 2,690,261 Maust Sept. 28, 1954 2,753,998Hardinge July 10, 1956

